Antarctic glaciers slipping swiftly seaward: scientists
GENEVA – Antarctic glaciers are melting faster across a much wider area than anyone ever thought before, say scientists.
The report Wednesday by thousands of scientists for the 2007-2008 International Polar Year concluded that the western part of the continent is also warming up, not just the Antarctic Peninsula, a narrow stretch pointing toward South America.
Making matters worse, scientists said the ice shelves that hold the glaciers back from the sea are also weakening.
Previously most of the warming was thought to occur on the Antarctic Peninsula, but satellite data and automated weather stations are indicating otherwise.
"The warming we see in the peninsula also extends all the way down to what is called west Antarctica," said Colin Summerhayes, executive director of the Britain-based Scientific Committee on Antarctic Research and a member of International Polar Year’s steering committee.
"That’s unusual and unexpected," he told The Associated Press.
West Antarctica is a vast land mass that lies along the Pacific Ocean over the South Pole. It includes the Antarctic Peninsula and is separated from the rest of the continent by the Ross and Weddell Seas.
For the International Polar Year, scientists from more than 60 countries have been conducting intense Arctic and Antarctic research over the past two southern summer seasons – on the ice, at sea, and via icebreaker, submarine and surveillance satellite.
The report Wednesday from Geneva was a broad summary of some of the main findings of the two years of research. Some of the findings have been released in partial reports earlier.
The big surprise was exactly how much western Antarctica’s glaciers are melting. The biggest of the western glaciers, the Pine Island Glacier, is moving 40 percent faster than it was in the 1970s, discharging water and ice more rapidly into the ocean, Summerhayes said.
The Smith Glacier, also in west Antarctica, is moving 83 percent faster than it did in 1992, he said.
The glaciers are slipping into the sea faster because the floating ice shelf that would normally stop them – usually 200 to 300 meters (650 to 980 feet) thick – is melting. And the glaciers’ discharge is making a significant contribution to the rise in sea levels.
"There are some people who fear that this is the first signs of an incipient collapse of the west Antarctic ice sheet," Summerhayes said. "If the west Antarctica sheet collapses, then we’re looking at a sea level rise of between 1 metre and 1.5 metres."
Together, all the glaciers in west Antarctica are losing a total of around 103 billion tons per year because the melting is much greater than the new snowfall, he said.
"That’s equivalent to the current mass loss from the whole of the Greenland ice sheet," Summerhayes said. "We didn’t realise it was moving that fast."
Summerhayes said sea levels will higher than predicted by the Intergovernmental Panel on Climate Change, a group set up by the United Nations.
A 2007 IPCC report predicted a sea level rise of 18 to 58 centimetres by the end of the century, which could flood low-lying areas and force millions to flee. The group said an additional 10 to 20 centimetres rise in sea levels was possible if the recent, surprising melting of polar ice sheets continues.
Ian Allison, co-chair of the International Polar Year’s steering committee, said many scientists now say the upper limit for sea level rises should be higher than the IPCC predictions.
"That has a very large impact," Allison said.
He also said extremely large storms that might previously have occurred once a year would start to occur on a weekly basis in some coastal areas of other continents.
Up until recently, scientists were even debating whether Antarctica was warming.
But Eric Steig of the University of Washington proved it was in a January report in the journal Nature. His study said Antarctica’s average annual temperature has increased by about 0.56 degrees Celsius (1 degree Fahrenheit) since 1957, but is still 45.6 degrees Celsius below zero.
Steig also found that autumn temperatures in east Antarctica were cooling over the long term.
International Polar Year researchers found that the southern ocean around Antarctica has warmed about 0.2 degrees Celsius in the past decade, double the average warming of the rest of the Earth’s oceans over the past 30 years.
AP / Expatica